That's some of the most poppy**** stuff I ever heard. Barbers stopped doing shaves with straights because of health codes and the fact most guys switched to electrics or cartridges and didn't need a barber to shave them anymore and the barbering schools did less and less to train them for shaving.
It's true barbers in the 40s and 50s especially, applied lather with their hands and used a latherking machine to dispense it which gave terrible lather. Barbers were taught when applying lather with their hands they could map out the beard growth. These days they would probably be using rubber gloves.
Keeping customers brush and mug in the shop goes way back to the early 20th century.